International Phone Number Formats

International telephone numbers have a standard format (more or less!), but the specific dialing codes vary from country to country. This information might help if you are having trouble figuring out the correct number to use for calling Calgary.

Each of the above dialing codes are known by other terms - e.g., 'international access code' is also called 'international dialing prefix' and 'IDD' (which stands for 'international direct dialing' code), among other terms.

Note that national access codes are another type of dialing code, but they aren't used for international calling. They are only used for long distance dialing within a country. They must be removed for international dialing or your call will not complete properly.

The 4 dialing codes are combined to form an international telephone number in this format.

Format of an International Phone Number

idd

ccc

aaa

nnn nnnn

internationalaccess code

countrycode

areacode

local subscribernumber

Below are details on each part of an international phone number, including a bit on national access codes, too.

International access codes are used to initiate a call to another country. They are the first digits dialed for an international call and they tell the phone company you need an open international line for your call.

International access codes are also sometimes called IDDs, 'international direct dial' codes, or international call prefixes.

The most commonly used international access code is '00' which is used by dozens of countries. However, many other numbers are used, too, such as '011', '001', and '020'.

In addition, there are many other types of variations in the access codes countries use. For instance:

Some countries have multiple codes (e.g., South Korea)

Some codes require a short dialing pause (noted by a '~') before continuing to dial (e.g., Georgia uses '8~10')

Some use special codes to indicate what phone carrier to use (e.g., Singapore)

Some use a different code if you are making a VoIP call (e.g., Indonesia) instead of a regular landline or mobile phone call

Some have special codes for calling neighboring countries (e.g., Kenya)

As well, many mobile providers use special character sequences to simplify international calling. For instance on many GSM phones, you can use the '+' key to initiate an international call, so you begin dialing the country code directly.

Country Codes

Country codes are used to indicate what country you are calling when placing an international call. The country code is normally indicated with a '+' such as +44 for UK, +1 for US, +91 for India. Country codes are also sometimes known as ISDs or 'international subscriber dialing' codes.

Country codes are used exclusively for international calls. They are never used to call another number within a country.

Most countries have unique country codes and most are either 2- or 3-digits long. In some cases, multiple countries share a single code - e.g., countries in the North America Numbering Plan [NANP] share the code '+1'. In such cases, unique area codes then serve to indicate the specific country being called.

National access codes are used to make long distance calls within a country. Not all countries use NDDs, but most do.

National access codes are also sometimes known as national direct dial codes, NDDs, or national call prefixes.

National access codes should not be used when making an international call to a country. If your dialing sequence includes the national access code, your call will fail.

Among countries that have national access codes, the most commonly used codes are '0' and '1'. However, many other codes are used, too, including '7', '8', '21', and '22'. As well, some countries use multiple codes to specify which service provider to use for the call (e.g., Singapore).

The rules for using national access codes are fairly complex and vary significantly around the world. Rules can also vary significantly even within a country - for instance, an access code may be required in some areas and not required in others.

At a very general level, it is fairly common for national access codes to be required when dialing from one area code to another and they are often not required for making calls between two numbers in the same area code. But since rules vary so much from place to place, you need to check with your local provider if you have questions.

Area codes are used to route calls within a country, typically to a certain city or region. Area codes are also sometimes known as STDs ('subscriber trunk dialing' codes) or city codes (although city codes may also refer to UN/LOCODE used for airport designations and other purposes).

Most countries use area codes, but there are a good number of smaller countries that make do without - for example: Bahrain, Denmark, and Haiti, among others.

In general, area codes are assigned to specific geographic regions within a country, such as a city, state, or province.

In earlier times, many regions had unique area codes and so area codes were an excellent predictor of where you were calling. However, as local populations and the number of phones in service has grown, many larger areas must now use multiple area codes so they don't run out of local phone numbers.

In some cases, these area codes now actually overlap so that next door neighbors can have different area codes. As well, with the advent of nationwide (and even international) mobile phone plans, many people keep phones even after they move to a new region. As a result, area codes, while still largely accurate in figuring out where someone lives, aren't quite as predictive as they used to be.

The rules for using area codes within countries are as complicated as the rules for using national access codes. We recommend that you check with your local provider to determine the rules in your area.

While area code usage rules are complicated within countries, they are very clear for international calling: you must include them! That is, if the country you are dialing uses them. If you leave out the applicable area code from your international dialing sequence, your call will not complete properly.

Local phone numbers, or local subscriber numbers are unique phone numbers assigned within an area code (or sometimes a country code). A local number directs a phone call to a specific location (e.g., a residence or business location) or handset, in the case of mobile phones.

The number of digits in a local number varies around the world - and even within a single country. To simplify things, efforts are underway to standardize the number of digits, at least within countries. Sometimes these efforts entail morphing the country's area codes and local number together to create numbers of uniform overall length. This is what is being done in India, for example, where area codes vary from 2-4 digits and local numbers from 6-8 digits. Their new numbering scheme makes all numbers conform to a uniform standard of 10 digits, including both the local number and the area code.